已知sinα=-根号5\5,则sin^4α-cos^4α的值帮下忙._数学解答

已知sinα=-根号5\5,则sin^4α-cos^4α的值
帮下忙.

人气：232 ℃　时间：2020-04-15 17:12:25

解答

sin^4α-cos^4α
=(sin²α+cos²α)(sin²α-cos²α)
=-cos(2α)
=2sin²α-1
=2*(-√5/5)²-1
=2*（1/5）-1
=-3/5